In general, entertainment, education, art and so forth (hereinafter collectively referred to as “content”) packaged in digital form offer higher audio and video quality than their analog counterparts. However, content producers, especially those in the entertainment industry, are still reluctant in totally embracing the digital form; the primary reason being that digital contents are particularly vulnerable to pirating. Unlike the analog form, where some amount of quality degradation generally occurs with each copy, a pirated copy of digital content is virtually as good as the “gold master.” As a result, much effort has been spent by the industry in developing and adopting techniques to provide protection for the distribution and rendering of digital contents.
Historically, the communication interface between a video source device (such as a personal computer) and a video-sink device (such as a monitor) is an analog interface. Thus, very little focus has been given to providing protection for the transmission between video sources and video sink devices. With advances in integrated circuits and other technologies, a new type of digital interface between video source and video sink devices is emerging. The availability of this type of new digital interface presents yet another new challenge to protecting digital video content. Similarly, production challenges exist for exchanges of status values between the video generating video source application and the video transmitting video hardware interface of the video source device.
In particular, protecting content displayed on systems capable of supporting multiple display outputs presents a serious problem. In such systems, it is necessary to ensure that premium content ends up on a desired output in which it can be protected. Moreover, some premium content may contain a restriction prohibiting it from being displayed on certain types of display devices (e.g., analog devices), which do not provide content protection. Although current methods for digital content protection can enable video hardware interfaces to securely transmit digital video to external video sink devices, these methods do not provide a simple mechanism for verifying that the content arrived at the protected display. Moreover, systems supporting multiple display outputs are subject to rewiring of input and output selection devices, such that rogue agents may (trivially) re-wire these input and output devices using software accessible chip registers in order to re-direct premium content streams to unprotected or undesired display devices.